The goal of the proposed research is to provide a genetic-based pharmacology for the study of synaptic and neural function. The tremendous diversity of toxins from the venoms of predatory Conus snail species provide a natural combinatorial-based pharmacology that can be used to selectively bind to the members of the large and diverse group of neurotransmitter receptors that mediate synaptic communication. We propose to use C. elegans to rapidly purify new toxins that will be of interest to the broad community of neurobiologists. We have three major aims. The first aim is to identify and purify peptide toxins from the venoms of Conus snails that disrupt the behavior of the soil nematode C. elegans by perturbing nervous system function. A long-term goal of this strategy is to use Conus toxins as specific probes that will permit the identification of new gene products that contribute to nervous system function. The second aim is to identify and purify peptide toxins that block specific ligand-gated currents in muscles and neurons of C. elegans. These toxins will be invaluable for C. elegans neurobiologists and will allow for detailed mechanistic studies of synaptic transmission in C. elegans that currently are not possible because of the lack of specific pharmacological agents to acutely block specific classes of currents. We will use genetic and electrophysiological strategies to determine the site and mechanism of action of the purified Conus toxins. We have also used tissue-specific promoters to express active Conus toxins in transgenic worms. The Conus Im1 toxin blocks approximately 50% of the ACh-gated current at the neuromuscular junction. The gene products that contribute to this Im1-sensitive current have not yet been identified. Using a new genetic strategy, we will identify gene products that are required for this portion of the synaptic cholinergic current. The tremendous diversity inherent in Conus peptides, the specific and potent receptor interactions, and the fact that these peptides can be expressed in transgenic organisms in a tissue specific manner, may in the future provide a framework for designing genetic-based therapies for neurological disorders.